Body support cushioning system with sideboard positioning mechanism

ABSTRACT

A cushion for uniformly distributing support of an invalid comprising a liquid container of flexible sheet material which is impervious to the liquid, and means to elevate side portions of the container to form a loose upper surface which can conform to the supported body portions of the invalid and support these portions as in flotation. For a constant volume of liquid in the container, the position of the side portions adjusts the depth to enable bodies of varying weight to be floated free of the underlying support surface. The means for varying the position of the sideboards applies maximum torque when the sideboards are in the horizontal position and maximum speed as the sideboards approach the vertical position.

United States Patent [191 Tenteris et al.

[ 51 Apr. 2, 1974 BODY SUPPORT CUSHIONING SYSTEM WITH SIDEBOARDPOSITIONING MECHANISM [75] Inventors: Ansis U. Tenteris, Toledo; BruceW.

Wetzel, Millbury, both of Ohio [73] Assignee: Jobst Institute, Inc.,Toledo, Ohio [22] Filed: Apr. 18, 1972 [21] Appl. No.: 245,157

[52] US. Cl 5/348 WB, 5/60 [51] Int. Cl A6lg 7/10, A47c 27/08 [58] Fieldof Search 5/18 R, 18 B, 61, 348,

[56] References Cited UNITED STATES PATENTS 3,585,660 6/197l Gottfriedet al. 5/348 R 3/1894 Karp 5/18 B X Primary Examiner-Bobby R. GayAssistant Examiner-Andrcw M. Calvert Attorney, Agent, or Firm-David H.Wilson [57] ABSTRACT A cushion for uniformly distributing support of aninvalid comprising a liquid container of flexible sheet material whichis impervious to the liquid, and means to elevate side portions of thecontainer to form a loose upper surface which can conform to thesupported body portions of the invalid and support these portions as inflotation. For a constant volume of liquid in the container, theposition of the side portions adjusts the depth to enable bodies ofvarying weight to be floated free of the underlying support surface. Themeans for varying the position of the sideboards applies maximum torquewhen the sideboards are in the horizontal position and maximum speed asthe sideboards approach the vertical position.

12 Claims, 3 Drawing Figures BODY SUPPORT CUSHIONING SYSTEM WITHSIDEBOARD POSITIONING MECHANISM SUMMARY OF THE INVENTION This inventionrelates to body supporting systems and particularly to cushioning meansfor supporting invalids and a support structure for the cushioning meanswith asideboard positioning mechanism.

A body support system of the type disclosed in U.S. Pat. No. 3,585,660entitled Body Support Cushioning System by Max Gottfried,. Dennis G.Mosiniak and Ansis V. Tenteris is utilized to avoid the occurrence ofbedsores or decubitus ulcers. Bedsores are usually attributed to theocculsion of the blood supply to areas of support of an invalid wherehigh pressures are developed as in the region of bony protuberances uponwhich the body weight is concentrated. In these regions when the surfacepressure exceeds the pressure distributing the lymph fluid, a starvationof the cells occurs. The above referenced patent teaches the utilizationof the principal of flotation to support an invalid. The invalid iseffectively floated in a pool of liquid which is isolated from theinvalid by a flexible material such as neoprene impregnated nylon whichpresents a loose interface between the supporting liquid pool and theinvalid. The material essentially conforms to the invalids body in amanner similar to that where the invalid is immersed directly in theliquid. Thusly the supporting force is evenly distributed over thesurface of the invalids body.

In order to minister to the invalid the sideboardsof the supportingapparatus are lowered and the supporting fluid flows to these sideportions thereby lowering the invalid to the underlying support. Manualpositioning of the sideboards presents two obvious difficulties. First asingle attendant can only operate one sideboard at a time. Since variouspositions are provided to adjust the depth of the pool the attendant mayhave to make several trips from one side of the bed to the other inorder to achieve the proper adjustment. The second disadvantage is thatit may be extremely hard for a relatively weak attendant to exert theforce required to lift a sideboard from the horizontal position.

The present invention-solves these difficulties by utilizing a sideboardpositioning mechanism. The positioning mechanism allows the attendantsimultaneous control of the sideboards and provides an infinite numberof intermediate positions between horizontal and vertical. Themechanical advantage of the mechanism greatly reduces the amount offorce required to raise the'sideboards from the horizontal position.

An object of the invention is to improve body support cushions forinvalids.

A second object is to facilitate the manipulation of a body supportcushion utilizing liquid for the supporting medium and thereforeinvolving a substantial weight of liquid.

A third object is to provide an infinite range of sideboard positions toenable adjustment in the depth of a liquid pool providing support for aninvalid.

In accordance with the above objects a feature of this invention ismechanical means for positioning the pivoted side panels of a supportfor a liquid filled body support cushion with relation to a horizontalbase such that a liquid impervious flexible envelope containing thesupporting fluid can conveniently be shifted in posi- 2 tion to adjustthe depth of the supporting pool of liquid.

Another feature resides in a positioning mechanism which has mechanicaladvantage which increases as the force required to control alteration ofposition increases. It is to be appreciated that the fluid nature, ofthe heavy liquid employed for displacement support of a body causes theweight of that liquid to follow the means which confines it. When sidepanels are lowered the liquid flows to the region of the panels imposingforces which must be overcome. In the case where the panels approach thehorizontal and the envelope for the liquid is of sufficient lateralextent to extend beyond the outer limits of the panels a pendantreservoir is formed and in extreme circumstances is suspended at theouter edges of the panels. This imposes essentially all of the weight ofthe supporting liquid at the maximum moment arm around the pivotalmounting of the panels and requires a very substantial mechanicaladvantage in the positioning mechanism to maintain the driving forces atreasonable levels. Such advantage is achieved by the relationship of thelength and location of pivoted linkages in the drive mechanism and themeans to shift the location of those pivots and to shift the moment offorce'around them as the loading is changed.

A further feature is the incorporation of a biasing meanscounterbalancing the liquid loading of the movable panels to facilitatethe movement of the panels by the drive mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective of a bodysupport system according to this invention showing an invalid floatingin a cushion;

FIG. 2 is a perspective of the system of FIG. 1 showing an invalidpositioned for treatment with the flotation pool dispersed to expose theinvalid; and

FIG. 3 is a front elevation of the sideboard positioning mechanism forone sideboard according to the invention with the linkage for theopposite sideboard brokenaway and omitted.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention isillustrated as applied to a bed. FIG. 1 depicts a body supportcushioning system such as the one shown in FIG. 1 of the abovereferenced Gottfried Patent. The bed 11 provides a cushioned support forthe entire body of an invalid 12 by in effect floating the invalid in apool of liquid, conveniently water. An envelope 13 for the liquid ismade up of liquid impervious flexible sheet material such as neoprenecoated nylon fabric fabricated into an upper and lower face 14 and 15joined at their margins in a liquid tight joint 16 shown in FIG. 2. Whenarranged as a full cushion for a bed 11, the envelope 13 is of a lengthslightly exceeding the length of the bed and a width exceeding the widthof the invalid by at least twice the depth of the pool of liquidrequired to float the invalid free of the underlying support surface.When the sides of the envelope 13 are raised and brought toward eachother the lower face 15 defines a cupped container for the flotationliquid while the upper face 14 has excess material available to confonnto the invalids body. When the invalid is raised free of the underlyingsupport as in FIG. 1 the free upper face 14 imposes the supporting forceof the liquid displaced by the invalid uniformly over the supportedregion of the body of the invalid thereby effectively floating thatregion.

The present system is arranged so that the envelope can be contained ina region that can be varied between that defining a pool which is wideand shallow and narrow and deep. While the envelope should be of suchdimensions as would minimize the volume of liquid required to separatethe inner surfaces of the faces 14 and 15, a large range of sizes ofinvalids must be accommodated by a given envelope. A thin person can befloated in a shallower pool of liquid than that required to float afatperson or a person having a thick body. The variation is accomplished byproviding a range of positions in which the longitudinal edges of theenvelope are maintained both as to-their lateral separation from eachother and their height above the underlying major area of envelopesupport.

In order to expose the patient for treatment or examination as in FIG. 2the upper face 14 of the envelope 13 which enfolds the patient must belowered relative to the underlying support. This is accomplished bymanipulating the pool of liquid so that the patient is gently lowered tothe supporting surface 22 beneath the lower face 15 of the envelope 13.Since the supporting liquid exceeds the patients weight it is asignificant load to be manipulated by nurses and attendants.

Manipulation of the liquid pool as between the conditions illustrated inFIGS. 1 and 2 is facilitated by the mounting for envelope 13. Aheadboard l7 and a footboard 18 to be described later are joined by siderails 19 secured thereto by brackets 21 to provide a rigid mounting forpreviously mentioned envelope support panel 22. Lateral restraint forthe envelope 13 is supplied by sideboards 23 extending between headboard17 and footboard 18. The parallel sideboards 23 are spaced at theirlower edges 24 at the minimum width dimension of the cushion. Thisdimension is dependent upon the maximum body width which is to beaccommodated for a maximum flotation pool depth.

The width and depth of the pool contained by envelope 13 may beregulated for a given volume of liquid by. the positioning of sideboards23. The sideboards 23 are pivoted about their lower edge 24 at headboardl7 and footboard 18. This may be accomplished by providing pivot rodextending from each end of the sideboards. The protruding stub ends ofrod 20 fit into sleeve bearings 30 in the headboard and footboard. Tangs6 are secured to pivot rods 20 as by welding and can be secured to thesideboard 23 by screws or other fasteners. The width of the pool variesas the angular relationship of the sideboards 23 to the support panel22. The cross-section of the pool therefore will vary from an invertedtruncated triangle when the sideboards are between the vertical andhorizontal to a rectangle when the sideboards are vertical. As thesideboards 23 vary from horizontal to vertical their longitudinal edgesremote from the pivot rod 20 and coupled to the envelope 13 are elevatedto increase the depth of the pool to its maximum depth when thesideboards 23 are perpendicular to the support panel 22.

In order to achieve and maintain a particular angular relationshipbetween the sideboards 23 and the support panel 22 a mechanism forpivoting the sideboards is enclosed in footboard l8. Advantageously themechanism can be as that shown in FIG. 3. The sideboards 23 pivot aboutpivot point 25 centered in bearing 30 in the footboard and headboard.Link arm 26 is firmly attached to sideboard 23 through pivot rod 20 atpivot point 25 and therefore moves through the same angle as doessideboard 23.

A threaded nut 27 is free to move along threaded shaft 28 journaled forrotation by means not shown in footborad 18. The advance ofnut 27 isdependent upon the direction the shaft is turned. Attached to thethreaded nut 27 at pivot point 29 is link arm 31. At the top of threadedshaft 28 is a fixed pivot point 32 for link arm 33. Link arm 31 and linkarm 33 are connected at pivot point 34 so that, for example, as threadednut 27 moves up threaded shaft 28 it causes. pivot points 29 and 34 tomove upward. Pivot point 34 is moved away from threaded shaft 28 sincelink arm 33 moves counter clockwise as viewed in FIG. 3 about pivotpoint 32 to move link arm 31 clockwise about pivot point 29.

As pivot point 34 moves away from threaded shaft 28 so does pivot point35 at the upper end of link arm 31. Pivot point 35 is attached to linkarm 36. Link arm 36 is connected to crank or link arm 26 at pivot point37. Pivot point 37 is constrained to movement in an are around pivotpoint 25 so the outward movement of link arm 36 causes crank 26 andsideboard 23 to rotate about pivot point 25 in a clockwise direction.This rotates the sideboard 23 clockwise to lower its edge remote frompivot rod 20 and reduce the depth of the pool. Of course, when threadednut 27 is moved down threaded shaft 28 the opposite motion occurs,sideboard 23 rotates in a counter clockwise direction, and the depth ofthe pool is increased. Advantageously, a torsion spring 38 may beattached to the footboard and sideboard in such a manner as tocounterbalance a portion of the weight of the liquid in envelope 13,thereby decreasing the force required to lift the sideboard andthusfacilitating operation of the mechanism.

Advantageously threaded shaft 28 may have a bevel gear 39 mounted at oneend and meshed with another bevel gear 41 which is turned by hand crank42 in FIGS. 1 and 2. In this manner a nurse or attendant may use thehand crank 42 to raise and lower sideboards 23 thereby controlling thedepth of the liquid in envelope 13.

Let us assume that sideboard 23 is in the horizontal position where theweight of the liquid resting upon it is the greatest. This weightproduces a moment M, about pivot point 25 in a clockwise direction. Inorder to balance the load a force must be applied at pivot point 37 in acounterclockwise direction to produce a moment on crank 26. If wedesignate this force as F, and apply in a direction parallel to the axisof link 36, then the force times the effective length L, of crank 26equals the moment on sideboard 23 or F X L M The effective length ofcrank 26 is determined by projecting a line through pivot points 35 and37 and measuring the perpendicular distance to pivot point 25.

The force F, is provided by a force applied on hand crank 42 andtransmitted through bevel gears 41 and 39, threaded shaft 28 andthreaded nut 27 such that a component F of the applied force isperpendicular to link 31 at pivot point 29. If we designate the distancebetween pivot points 29 and 34 as L then there is a moment F X L aboutpivot point 34. The perpendicular distance between link 36 and pivotpoint 34 is the effective length L of the distance between pivot points34 and 35. Therefore in order to balance the-moments about pivot point34 a force F is produced at pivot point 35 parallel to link 36 in acounter clockwise direction and F L F X L;,.

Also produced by the force on the hand crank 42 is a force component atpivot point 29 parallel to link 31. This force component acts upon link36 at pivot point 35 to produce a force component F parallel to link 36and in the same direction as F Thus the combination of F and F producesF or'F P F As the sideboard 23 is rotated toward the vertical positionthe moment M, decreases since the weight of liquid decreases as it flowstoward the longitudinal center of the cushion system and the effectivelength of the moment arm decreases. Since link 31 is rotating in acounter clockwise direction about pivot point 34 the force component Fdecreases therefore decreasing F and in turn F Thus a constant force athand crank 42 produces maximum torque when sideboard 23 is in ahorizontal position and decreasing torque as the sideboard is rotated tothe vertical position. It is evident that if an increase in maximumtorque is required it may be achieved by increasing the length of crank26 or decreasing the distance between pivot points 34 and 35 orincreasing the distance between pivot points 29 and 34 or anycombination thereof.

The constant force input to the system is particularly advantageouswhere it is desired to drive the bevel gear with an electric moter. Eachtype of motor has a particular point on its performance curve where itis operating at maximum efficiency..Thus it would be desirous to operateat that point in order to be able to utilize the smaller and leastexpensive motor available. Looking at links 31 and 33 it can be seenthat as threaded nut 27 is moved down threaded shaft 28 in equalincrements the distance between pivot point 34 and the shaft becomessmaller by increasing increments. These increasing increments ofhorizontal movement are reflected through link 36 to crank 26. Therethey are trans formed into increasing increment of rotational movementabout pivot point 25. Thus as the threaded shaft 28 is turned at aconstant speed the speed of rotation of sideboard 23 increases from thehorizontal to the vertical position. Since the torque required toproduce the movement is decreasing as the load decreases, the powerrequired remains constant. Therefore the power input to the systemremains constant and the motor operates at maximum efficiency.

While the overall dimensions of the system will depend upon the spaceavailable and the maximum load required to be lifted, certain relationsmust be maintained. In order to avoid locking up or over-centerconditions the distance between pivot points 29 and 34 and pivot points34 and 32 must be greater than the maximum distance desired betweenpivot points 29 and 32. Also the distance between pivot points 25 and 37and pivot points 37 and 35 must be greater than the maximum straightline distance between pivot points 25 and 35 when the sideboard 23 is inits vertical position. Fi-

. nally the distance between pivot points 34 and 35 and pivot points 35and 37 must be greater than the straight line distance between pivotpoints 34 and 37 when the sideboard is in its horizontal position.

Exemplary geometry of the drive linkage involves a load moment imposedon sideboard 23 around the fixed pivot 25 and a drive moment imposedthrough crank arm 26 at coupling point 37 which can move in a fixed arcof radius defined by link 26 about fixed pivot 25. A second fixed arc ofmotion is that of the fulcrum or pivoted coupling point 34 about fixedpivot 32, that arc having a radius defined by link 33. A broken linkhaving a toggle-like action is made up of link 36 and link 31 pivotallycoupled at 35. When the sideboard pivot is twelve inches from the axisof screw 28, the effective radius of the first arc (link 33) is sixinches and the second arc (link 26) is four and one quarter inches, andwhen the effective length oflink 36 is eight and one quarter incheswhile the space between pivots 29 and 34, along link 31 is three andthree-eighths inches and between pivots 34 and 35 is four andfiveeighths inches, link 26 pivots around 25.9 for a displacement ofpivot 29 from a location six inches below pivot 32 to a position six andone half inches below pivot 32. Successive half-inch increments ofdisplacement downward increase the arc of counter clockwise displacementof link 26 to approximately l0.5, 12, 14 and 21. In such an arrangementa three-inch displacement of pivot 29 toward a position in which links33 and 31 approach a straight line'relationship results in a pivotaldisplacement of link 26 of about 76. It is advantageous to locatesideboard 23 about 30 clockwise from link 26 in such an arrangement sothat with pivot 29 six inches below pivot 32 sideboard 23 is essentiallyhorizontal.

If desired the lifting mechanism-enclosed in endboard 18 may be ahydraulic or electric motor. The linkages can be changed in length andtheir angular relationships to alter the mechanical advantage theyoffer. Ac-

cordingly, it is to be understood that the above embodiments arepresented as illustrative and are not to be read as imposing limitationson the invention.

We claim:

- 1. A cushioning system for invalids comprising an envelope of aflexible, liquid impervious, sheet material closed upon itself to form acontainer for liquid, said container having a lateral extent greaterthan the portion of the invalid to be supported; a body of liquid withinsaid envelope upon which a portion of the invalid is supported at leastin part by displacement of said liquid; a support for said envelopeincluding a horizontal region adapted to support a major face of saidenvelope; an endboard perpendicular to said horizontal region and havingspaced generally parallel major faces; first and second opposedsideboards extending upwardly from said horizontal support; a pivotalmounting for at least one of said sideboards for pivotal motion aroundan axis adjacent and generally parallel to said horizontal support andperpendicular to said endboard, said envelope being coupled to portionsof said sideboards remote from said pivotal mounting; lever arm meansenclosed between said spaced major faces of said endboard and coupled tosaid pivotal mounting for pivotal motion around said axis; and meansenclosed between said spaced major faces of said endboard to drive saidlever arm means and thereby to drive said one sideboard about saidpivotal mounting.

2. A combination according to claim 1 in which said drive means includesmeans to maintain said sideboard at any of a selected plurality ofinclinations with respect to said horizontal support.

3. A combination according to claim 2 including a second pivotalmounting for said second sideboard along a second axis adjacent saidhorizontal support and generally parallel to said pivot axis ofsaidfirst sideboard; second lever arm means enclosed between said spacedmajor faces of said endboard and coupled to said second pivotal mountingfor pivotal motion around said axis; and means to couple said drivemeans to said second lever arms means whereby said drive means drivessaid second sideboard about its respective pivot mounting simultaneouslywith the driving of said first sideboard.

4. A cushioning system for invalids comprising an envelope of a flexibleliquid impervious, sheet material closed upon itself to form a containerfor liquid, said container having a lateral extent greater than theportion of the invalid to be supported; a body of liquid within'saidenvelope upon which a portion of the invalid is supported at least inpart by displacement of said liquid; a support for said envelopeincluding a horizontal region adapted to support a major face of saidenvelope; first and second opposed sideboards extending upwardly fromsaid horizontal support; a pivotal mounting for at least one of saidsideboards for pivotal motion around an axis adjacent and generallyparallel to said horizontal support, said envelope being coupled toportions of said sideboards remote from said pivotal mounting; means todrive said one sideboard about said pivotal mounting; andcounterbalancing means which aid said driving means when said portion ofsaid sideboard remote from said pivotal mounting is being raised andwhich oppose said drive means when said portion of said sideboard remotefrom said pivotal mounting is being lowered.

5. A combination according to claim 4 in which said counterbalancingmeans is a torsion spring.

6. A cushioning system for invalids comprising an envelope of a flexibleliquid impervious, sheet material closed upon itself to form a containerfor liquid, said container having a lateral extent greater than theportion of the invalid to be supported; a body of liquid within saidenvelope upon which a portion of the invalid is supported at least inpart by displacement of said liquid; a support for said envelopeincluding a horizontal region adapted to support a major face to saidenvelope; first and second opposed sideboards extending upwardly fromsaid horizontal support; a pivotal mounting for at least one of saidsideboards for pivotal motion around an axis adjacent and generallyparallel to said horizontal support, said envelope being coupled toportions of said sideboards remote from said pivotal mounting; means todrive said one sideboard about said pivotal mounting; and means includedin said drive means to decrease the torque applied to and increase thespeed of said sideboard for a given applied power as it is pivoted froma position of maximum load to a position of minimum load.

7. A combination according to claim 1 in which said drive means isactuated by a manual crank.

8. A support for an envelope of a flexible, liquid impervious, sheetmaterial closed upon itself to form a container for liquid, andproviding cushioning for a body by displacement of said liquidcomprising a primary panel adapted to be mounted with the plane of itsmajor face'horizontal, an end panel mounted perpendicular to saidprimary panel, first and second side panels, pivotal mounting means formounting a side panel for pivotal movement around a longitudinal edgeadjacent the major face of said primary panel and for shifting theelevation of a second longitudinal edge relative to the plane of saidprimary panel, drive means arranged to decrease the torque applied tosaid side panel tending to pivot it around said mounting means and toincrease the speed of arcuate motion of said sideboard for a givenapplied power as said side panel is pivoted from a generally horizontalposition toward a vertical position, and means to apply operating powerto said drive means.

9. A combination according to claim 8 wherein said drive means comprisesa lead screw, a nut on said lead screw, a first drive link pivotallycoupled at one end to said nut, a second drive link pivotally coupled tothe first drive link at a point remote from said nut, a third linkdefining a fixed arc of motion at a point along its length and having afixed pivot in proximity to the axis of said lead screw and spaced fromsaid nut, a fulcrum from said fixed arc defined by said third link forsaid first drive link and coupled to said first drive link between saidnut and the pivotal coupling to said second drive link, and a crank armextending from said pivotally mounted side panel and pivotally coupledto said second drive link at a point spaced from the pivotal couplingbetween said first and second drive links.

10. A support for an envelope of a flexible, liquid impervious, sheetmaterial closed upon itself to form a container for liquid, andproviding cushioning for a body by displacement of said liquidcomprising a primary panel adapted to be mounted with the plane of itsmajor face horizontal, an end panel mounted perpendicular to saidprimary panel. first and second side panels, means mounting said sidepanels with a first longitudinal edge adjacent the major face of saidprimary panel and a second longitudinal edge adapted to be elevated fromthe plane of major face of said primary panel, and a system of leversenclosed in said end panel adapted to alter the elevation of said secondlongitudinal edge of at least one panel with respect to the plane of themajor face of said primary panel.

11. A combination according to claim 10 wherein said first longitudinaledges are spaced and parallel on said major face of said primary paneland a pivotal mounting for said side panels at said first longitudinaledges.

12. A combination according to claim 9 wherein the effective length ofsaid second drive link and said crank between their respective pivotalcouplings approximates the spacing of said pivotal mounting means fromthe axis of said screw, the radius defined by said third linkapproximates one half the spacing of said pivotal mounting means fromthe axis of said screw, and the length of the first drive link exceedsthe length of said third link.

1. A cushioning system for invalids comprising an envelope of aflexible, liquid impervious, sheet material closed upon itself to form acontainer for liquid, said container having a lateral extent greaterthan the portion of the invalid to be supported; a body of liquid withinsaid envelope upon which a portion of the invalid is supported at leastin part by displacement of said liquid; a support for said envelopeincluding a horizontal region adapted to support a major face of saidenvelope; an endboard perpendicular to said horizontal region and havingspaced generally parallel major faces; first and second opposedsideboards extending upwardly from said horizontal support; a pivotalmounting for at least one of said sideboards for pivotal motion aroundan axis adjacent and generally parallel to said horizontal support andperpendicular to said endboard, said envelope being coupled to portionsof said sideboards remote from said pivotal mounting; lever arm meansenclosed between said spaced major faces of said endboard and coupled tosaid pivotal mounting for pivotal motion around said axis; and meansenclosed between said spaced major faces of said endboard to drive saidlever arm means and thereby to drive said one sideboard about saidpivotal mounting.
 2. A combination according to claim 1 in which saiddrive means includes means to maintain said sideboard at any of aselected plurality of inclinations with respect to said horizontalsupport.
 3. A combination according to claim 2 including a secondpivotal mounting for said second sideboard along a second axis adjacentsaid horizontal support and generally parallel to said pivot axis ofsaid first sideboard; second lever arm means enclosed between saidspaced major faces of said endboard and coupled to said second pivotalmounting for pivotal motion around said axis; and means to couple saiddrive means to said second lever arms means whereby said drive meansdrives said second sideboard about its respective pivot mountingsimultaneously with the driving of said first sideboard.
 4. A cushioningsystem for invalids comprising an envelope of a flexible liquidimpervious, sheet material closed upon itself to form a container forliquid, said container having a lateral extent greater than the portionof the invalid to be supported; a body of liquid within said envelopeupon which a portion of the invalid is supported at least in part bydisplacement of said liquid; a support for said envelope including ahorizontal region adapted to support a major face of said envelope;first and second opposed sideboards extending upwardly from saidhorizontal support; a pivotal mounting for at least one of saidsideboards for pivotal motion around an axis adjacent and generallyparallel to said horizontal support, said envelope being coupled toportions of said sideboards remote from said pivotal mounting; means todrive said one sideboard about said pivotal mounting; andcounterbalancing means which aid said driving means when said portion ofsaid sideboard remote from said pivotal mounting is being raised andwhich oppose said drive means when said portion of said sideboard remotefrom said pivotal mounting is being lowered.
 5. A combination accordingto claim 4 in which said counterbalancing means is a torsion spring. 6.A cushioning system for invalids comprising an envelope of a flexibleliquid impervious, sheet material closed upon itself to form a containerfor liquid, said container having a lateral extent greater than theportion of the invalid to be supported; a body of liquid within saidenvelope upon which a portion of the invalid is supported at least inpart by displacement of said liquid; a support for said envelopeincluding a horizontal region adapted to support a major face to saidenvelope; first and second opposed sideboards extending upwardly fromsaid horizontal support; a pivotal mounting for at least one of saidsideboards for pivotal motion around an axis adjacent and generallyparallel to said horizontal support, said envelope being coupled toportions of said sideboards remote from said pivotal mounting; means todrive said one sideboard about said pivotal mounting; and means includedin said drive means to decrease the torque applied to and increase thespeed of said sideboard for a given applied power as it is pivoted froma position of maximum load to a position of minimum load.
 7. Acombination according to claim 1 in which said drive means is actuatedby a manual crank.
 8. A support for an envelope of a flexible, liquidimpervious, sheet material closed upon itself to form a container forliquid, and providing cushioning for a body by displacement of saidliquid comprising a primary panel adapted to be mounted with the planeof its major face horizontal, an end panel mounted perpendicular to saidprimary panel, first and second side panels, pivotal mounting means formounting a side panel for pivotal movement around a longitudinal edgeadjacent the major face of said primary panel and for shifting theelevation of a second longitudinal edge relative to the plane of saidprimary panel, drive means arranged to decrease the torque applied tosaid side panel tending to pivot it around said mounting means and toincrease the speed of arcuate motion of said sideboard for a givenapplied power as said side panel is pivoted from a generally horizontalposition toward a vertical position, and means to apply operating powerto said drive means.
 9. A combination according to claim 8 wherein saiddrive means comprises a lead screw, a nut on said lead screw, a firstdrive link pivotally coupled at one end to said nut, a second drive linkpivotally coupled to the first drive link at a point remote from saidnut, a third link defining a fixed arc of motion at a point along itslength and having a fixed pivot in proximity to the axis of said leadscrew and spaced from said nut, a fulcrum from said fixed arc defined bysaid third link for said first drive link and coupled to said firstdrive link between said nut and the pivotal coupling to said seconddrive link, and a crank arm extending from said pivotally mounted sidepanel and pivotally coupled to said second drive link at a point spacedfrom the pivotal coupling between said first and second drive links. 10.A support for an envelope of a flexible, liquid impervious, sheetmaterial closed upon itself to form a container for liquid, andproviding cushioning for a body by displacement of said liquidcomprising a primary panel adapted to be mounted with the plane of itsmajor face horizontal, an end panel mounted perpendicular to saidprimary panel. first and second side panels, means mounting said sidepanels with a first longitudinal edge adjacent the major face of saidprimary panel and a second longitudinal edge adapted to be elevated fromthe plane of major face of said primary panel, and a system of leversenclosed in said end panel adapted to alter the elevation of said secondlongitudinal edge of at least one panel with respect to the plane of themajor face of said primary panel.
 11. A combination according to claim10 wherein said first longitudinal edges are spaced and parallel on saidmajor face of said primary panel and a pivotal mounting for said sidepanels at said first longitudinal edges.
 12. A combination according toclaim 9 wherein the effective length of said second drive link and saidcrank between their respective pivotal couplings approximates thespacing of said pivotal mounting means from the axis of said screw, theradius defined by Said third link approximates one half the spacing ofsaid pivotal mounting means from the axis of said screw, and the lengthof the first drive link exceeds the length of said third link.